Cylindrical leak-resistant, thermoplastic coated, paperboard container

ABSTRACT

A generally cylindrical, thermoplastic coated, paperboard container having a leak-resistant, flat-bottomed structure, formed from a side seamed, thermoplastic coated paperboard blank having a plurality of alternating tapered fingers and angular fingers on one of its edges, the tapered fingers and angular fingers being separated by triangular gusset panels foldably connected to the fingers by score lines in the blank, the angular fingers being adapted to abut on the bottom, exterior surface of the container with a flat profile and the tapered fingers being adapted to overlap on the bottom, interior surface of the container to seal the bottom of the container.

United States Patent 1 1 Carlson Aug. 26, 1975 [75] Inventor: RichardWarren Carlson, Warwick,

[73] Assignee: International Paper Company, New

York, NY.

22 Filed: Aug. 19, 1974 21 Appl. NO.2 498,571

2.09l,29l 8/l937 Ringler 229/41 C UX 3,768,720 10/1973 Bundy 229/4l C X3,773,246 1 [/1973 Tyrseck 229/41 C X Primary E.\'aminerDavis T.Moorhead Attorney, Agent, orFirm-Ronald A. Schapira [57] f ABSTRACT Agenerally cylindrical, thermoplastic coated, paperboard container havinga leak-resistant, flat-bottomed structure, formed from a side seamed,thermoplastic coated paperboard blank having a plurality of alternatingtapered fingers and angular fingers on one of its edges, the taperedfingers and angular fingers being separated by triangular gusset panelsfoldably connected to the fingers by score lines in the blank, theangular fingers being adapted to abut on the bottom, exterior surface ofthe container with a flat profile and the tapered fingers being adaptedto overlap on the bottom, interior surface of the container to seal thebottom of the container.

16 Claims, 7 Drawing Figures CYLINDRICAL LEAK-RESISTANT, THERMOPLASTICCOATED, PAPERBOARD CONTAINER BACKGROUND OF THE INVENTION This inventionrelates to generally cylindrical, coated, paperboard containers for aliquid, paste, or frozen material. This invention is particularlyconcerned with a bottom construction for such containers having asubstantially flat profile, whereby the container will stand stably onflat surfaces without rocking or tipping over. This invention is alsoparticularly concerned with providing such a bottom construction whichwill be leak-resistant, so that the contents of the container will notleak out of the container or seep into the paperboard base stock,thereby weakening the paperboard and destroying the integrity of thecontainer. This invention is further particularly concerned withproviding such a container for relatively heavy loads, on the order ofabout 25 to 50 pounds.

Generally cylindrical, coated paperboard containers having bottomconstructions formed from abutting or overlapping fingers are well knownin the art. The bottom constructions in such containers have not,however, been entirely satisfactory for providing a leakresistant,flat-bottomed container for relatively heavy loads of liquids, pastesand frozen materials. One reason for this has been that such bottomconstructions have tended to be weak and prone to leak. This situationhas required that additional sealant members and sealant materials beused to supplement the overlapping or abutting fingers in the bottom ofthe containers. See, for example, US. Pat. Nos. 1,866,496, 1,867,914,2,160,488, and 2,097,893. Another reason has been that such bottomconstructions have had to be recessed in order to assure that thecontainer is stable when placed on a flat surface, the overlappingfingers tending to make the bottom constructions uneven and henceunstable. This has made such containers undesirable for use withrelatively heavy loads. See, for example, US. Pat. Nos. 1,362,090,1,867,914, 1,904,365, 1,443,280 and 2,097,893. Still another reason hasbeen that the bottom constructions have been quite prone to fail due towicking of a fluid product into exposed portions of the paperboard basestock. Bottom constructions formed from a plurality of over-lappingpaperboard fingers have heretofore invariably contained relatively largeareas of exposed paperboard at the edges of the fingers. These exposedareas of paperboard have generally been left unprotected by the surfacecoatings applied to the paperboard. Due to the problem of wicking, thelikelihood of failure of prior, cylindrical containers has been quitehigh, particularly when such containers have been utilized for storingliquids, pastes or frozen materials over a relatively long period oftime.

SUMMARY OF THE INVENTION In accordance with this invention, in athermoplastic coated, paperboard container provided with a generallycylindrical side wall, an improved bottom construction is provided whichcomprises a plurality of abutting, angular fingers on the bottom,exterior surface of the container; and a plurality of overlapping,tapered fingers on the bottom, interior surface of the container; eachof said angular fingers and said tapered fingers being separated by andfoldably connected to a triangular gusset panel; and said fingers beingfoldably connected to the cylindrical side wall of the container. Inaccordance with a second aspect of this invention, a thermoplasticcoated, paperboard blank, which can be formed into the generallycylindrical, flat-bottomed container of this application, includes asubstantially rectangular panel; a plurality of angular fingers; and aplurality of tapered fingers; each of said angular fingers and saidtapered fingers being separated by and foldably connected to atriangular gusset panel; and each of said fingers being foldablyconnected to one edge of said rectangular panel.

By this invention, a bottom construction for a generally cylindrical,flat-bottomed, leak-resistant container is provided which can beexpeditiously formed by conventional mass production techniques andwhich is adapted for storing relatively large quantities of liquids,pastes and frozen materials over a relatively long period of time.

DESCRIPTION OF THE DRAWINGS FIG. I is a plan view of a blank which canbe formed into the cylindrical, leak-resistant, thermoplastic coated,paperboard container of this invention.

FIG. 2 is a fragmentary, side elevational view of a cylinder, formed byside-seaming the blank of FIG. 1.

FIG. 3 is a fragmentary, side elevational view of the cylinder of FIG;2, the lower portions being urged inwardly of the cylinder to form thebottom construction of this invention.

FIG. 4 is a side elevational view showing the forming and sealing of thebottom of the cylinder of FIG. 3 to form the container of thisinvention.

FIG. 5 is a fragmentary, perspective view of the bottom exterior of thecontainer formed from the blank of FIG. 1.

FIG. 6 is a sectional view, taken along line 66 in FIG. 5, showing thebottom interior of the container formed from the blank of FIG. 1.

FIG. 7 is a fragmentary, sectional view, taken along line 7-7 inFIG 6,of the bottom construction of the container of FIGS. 5 and 6.

DETAILED DESCRIPTION OF THE INVENTION This application relates to agenerally cylindrical, leak-resistant, thermoplastic coated, paperboardcontainer formed from a blank, generally 10, shown in FIG. 1. The blank10 includes a substantially rectangular panel 1 La plurality of angularfingers 12, and a plurality of tapered'fingers 13. Each of the angularfingers 12 and the tapered fingers 13 is separated by and foldablyconnected "to a triangular gusset panel 14. Each of the angular fingersl2 and tapered fingers 13 is also foldably connected to a first edge 11aof the rectangular panel 1 l.

The paperboard blank 10 can be formed from any conventional,thermoplastic-coated, paperboard base stock. For example, the blank 10can be formed from a paperboard base stock coated on one or bothsurfaces with a polyolefin, such as polyethylene or polypropylene;saran, i.e., polyvinylidine chloride; an ethyleneacrylic acid copolymer;or a Surlyn ionic copolymer. The blank 10 is preferably coated on bothsurfaces with a polyolefin, particularly low density polyethylene.

In the blank 10, the thickness of the thermoplastic coating is notcritical, and any thickness greater than about 0.0005 inches, sufficientto enable a plastic to plastic bond to be formed between thethermoplastic coatings on the surfaces of the blank 10, can be suitablyutilized. Preferably, the thickness of the thermoplastic coatings on thesurfaces of the blank is from about 0.0010 inches to about 0.0020inches, particularly a thickness between about 0.0010 inches and 0.0015inches.

Also in the blank 10, any paperboard base stock conventionally utilizedin coated, paperboard containers can be utilized. Preferably, thepaperboard base stock has a basis weight of from about 150 pounds toabout 400 pounds per 3,000 sq. ft. and a thickness of about 0.010 inchesto about 0.030 inches. It is especially preferred that a paperboard basestock of about 325 to about 340 pounds per 3,000 sq. ft. and of about0.024 to about 0.028 inches thickness be utilized, particularly apaperboard base stock having a basis weight of about 333 pounds per3,000 sq. ft. and a thickness of about 0.026 inches.

In the blank 10, the angular fingers 12 and the tapered fingers 13 arefoldably connected to the triangular gusset panels 14 and to therectangular panel 11 along a plurality of score lines, generally 15, inthe blank 10. The score lines 15 define the first rectangular panel edge11a, as well as the foldably connected, abutting edges of the angularfingers 12, the tapered fingers 13 and the triangular gusset panels 14.The size and configuration of the individual score lines 15 in the blank10 are not critical, and any conventional dimensions and configurationsfor score lines in blanks for paperboard containers can be utilized.Preferably, the score lines 15 are formed to a depth of about 0.006 toabout 0.0085 inches in the blank 10.

In the blank 10, the exact size and configuration of the substantiallyrectangular panel 11, the angular fingers 12, the tapered fingers 13 andthe triangular gusset panels 14 are also not critical. However, as shownin the drawings and as will be discussed hereinafter, the elements ofthe blank 10 preferably have a size and configuration adapted tocooperatively provide a container having: a generally cylindrical sidewall formed from the generally rectangular panel 11; a bottom, exteriorsurface having a fiat profile, formed by abutting, angular fingers 12;and a bottom, interior surface which is sealed and reinforced byoverlapping, tapered fingers 13 and by triangular gusset panels 14,which are foldably attached to and horizontally aligned between theangular fingers l2 and the tapered fingers 13.

Preferably, the first rectangular panel edge 11a and the opposite edgeof the rectangular panel 11, i.e. the second rectangular panel edge llbdescribe concentric curves, rather than parallel straight lines, and theradius of curvature of the first edge 11a is somewhat smaller than theradius of curavature of the second edge 11b. This results in the sidewall of the preferred container of this invention being tapered inwardlyfrom its top to its bottom, rather than being vertical. The tapered sidewall of the resulting container constitutes a means for nesting aplurality of such containers.

In the blank 10, each of the angular fingers l2 preferably defines apentagon. As seen in FIG. 1, a first side or edge 12a of the pentagonabuts the first rectangular panel edge 11a and each of the second andthird sides or edges 12b and 120 of the pentagon, adjacent the firstpentagon edge 12a, abuts a first side or edge 14a of a triangular gussetpanel 14. It is particularly preferred that the remaining two sides oredges 12d and l2e of each pentagonal, angular finger 12 be of equallength and that the two remaining edges 12d and l2e include an anglesuch that the sum of the angles included by the two remaining edges 12dand 122 in all the angular fingers totals 360 In this way, all thepentagonal angular fingers 12 will abut on the exterior surface of thebottom construction formed in accordance with this invention. The numberof angular fingers of pentagonal configuration is not critical, and anynumber greater than three can be suitably utiilized. However it ispreferred that between five and eight angular fingers, especially sixangular fingers, be utilized. It is also preferred that all of theangles included between the two remaining edges 12d and 12:: of thepentagonal, tapered fingers 12 be the same, e.g., 60 when six angularfingers 12 are utilized. so that all the angular fingers will abut atthe center of the resulting container.

In the blank 10, each of the tapered fingers 13 preferably defines afigure of at least four edges, such as a square, a pentagon, a hexagon,a truncated ellipse, etc., a hexagon being particularly preferred. Asseen in FIG. 1, a first side or edge 13a of the hexagon abuts the firstrectangular panel edge 11a, and each of the second and third sides oredges 13b and 13c of the hexagon, adjacent the first tapered finger edge13a, abuts a second side or edge 14b of a triangular gusset panel 14. Itis particularly preferred that the remaining edge or edges 13d, 13e,13f, etc. of the tapered fingers l3 define a sufficiently large area sothat a portion of the tapered fingers 13 will overlap on the interiorsurface of the container bottom construction, formed in accordance withthis invention. In this regard, the extent to which the tapered fingersoverlap in the formed container is not critical. However, as shown inFIG. 1, it is preferred that the area of the tapered fingers 13 be suchthat only a minor portion of each tapered finger is in overlappingrelationship with other tapered fingers. As also shown in FIG. 1, it isparticularly preferred that one of the tapered fingers 13' be longerthan the other tapered fingers, as measured from its first edge 130, sothat the one, longer tapered finger will overlie the center of thebottom construction in the formed container, besides being overlapped oroverlapping other, tapered fingers 13.

As shown in FIG. 1, in the blank 10, the triangular gusset panels 14preferably have the same size and configuration to assure that theinside and outside of the bottom construction of the formed container isas flat as possible. It is also preferred that the angle includedbetween the first and second triangular gusset panel edges 14a and 14bbe the same, i.e., equal to 360 divided by the number of triangulargusset panels 14. For example, when twelve gusset panels are utilized,the angle between the first and second gusset panel edges 14a and 14b ineach triangular gusset panel 14 should be 30.

The blank 10 further includes a substantially rectangular edge portion16 foldably connected along the score line 15 to the first rectangularpanel edge 1 1a and to a second triangular gusset panel edge 14b. Theedge portion 16 is located adjacent a first edge 10a of the blank 10. Asurface of the rectangular edge portion 16 is adapted to be bonded,e.g., heat-sealed or adhesively secured, to a surface of the taperedfinger 13 adjacent an opposite edge 10b of the blank 10.

As a first step in forming'the generally cylindrical, leak-resistantpaperboard container of this invention, the blank 10 is side seamedalong the entire length of the first blank edge a. In side seaming theblank 10,

a surface of the edge portion 16 is bonded to a surface of the taperedfinger 13 adjacent the opposite blank edge 10b, and a surface of therectangular panel 11 adjacent the first blank edge 10a is bonded to asurface of the rectangular panel 11 adjacent the oppositeblank edge 10b.A cylinder 17, shown in FIG. 2, is formed by this step. The surfaces ofthe blank 10 can be bonded together to form the cylinderl7 by anyconventional method, as for example, by heatsealing or adhesive bonding.Preferably, the surfaces of the blank 10 are bonded together by forminga conventional, heatsealed, side seam bond between the thermoplasticcoatings on the surfaces of the paperboard base stock. As shown in FIG.2, the cylinder 17 is preferably formed faces of the angular fingers 12.At the same time, the

upper surfaces of the angular fingers 12 are heatsealingly pressedagainst the lower, overlying surfaces of the triangular gusset panels14.

The container, generally 23, formed by the use ofthe pressing means 18and the irons l9 and 20 is shown in FIGS. 5, 6 and 7.

from the blank 10 by bonding a surface of the rectanguopposite blankedge l0band bonding a surface of the rectangular panel 1 1, adjacent thefirst blank edge 10a, to an underlying surface of the rectangular panel11, adjacent the opposite blank edge 10b.

Schematically shown in FIG. 3 is the second step in forming thecontainer of this invention. The angular fingers 12, the tapered fingers13 and the triangular gusset panels 14 are urged upward and radiallyinward of the cylinder 17 by a means 18, pressing simultaneously uponthese fingers and gusset panels. As urged inwardly and upwardly by thepressing means 18, the angular and tapered fingers 12 and 13 fold aboutthe score line between these fingers and the first rectangular paneledge 1 la. In this step, the angular and tapered fingers and thetriangular gusset panels also fold about the score lines separatingthem. As folded, the tapered fingers l3 overlie the angular fingers l2,and the triangular gusset panels 14 lie between the angular fingers 12and the tapered fingers 13, the fingers 12 and 13 and gusset panels 14preferably being positioned substantially about the plane defined by thefirst rectangular panel edge 11a. A preferred means 18 for urging thefingers and gusset panels 12, 13 and 14 radially inward and upward,whereby the tapered fingers 13 properly overlie the triangular gussetpanels 14 and the angular fingers 12 about the plane of the firstrectangular panel edge 11a, is a means pressing only the tapered fingersl3 simultaneously inward and upward.

The last step in forming the container of this invention isschematically shown in FIG. 4. After the angular fingers l2, taperedfingers l3 and triangular gusset panels 14 have been urged radiallyinward of the cylinder 17, the fingers 12 and 13 and gusset panels 14are bonded together. It is preferred that the fingers and gusset panelsbe bonded together by forming intimate, plastic to plastic bonds betweenthe thermoplastic coatings on their surfaces. Such plastic to plasticbonds are preferably formed by heat-sealing the fingers and gussetpanels 12, 13 and 14 together, preferably by urging heated irons l9 andagainst the fingers l2 and 13 and the gusset panels 14. One of the irons19 heatsealingly presses downwardly, through the cylinder 17, againstthe upper surface of the fingers and gusset panels. At the same time,the other iron 20 heat-sealingly presses upwardly against the lowersurfaces of the fingers and gusset panels. For this purpose, the ironsl9 and 20 preferably have substantially flat, heated faces 21 and 22,with an area conforming to the bottom area of the cylinder 17. By thisstep, all of the lower surfaces As seen in FIG. 5, the container 23includes a generally cylindrical side wall 24 and a bottom construction,generally 25. The bottom 25 comprises a plurality of abutting, angularfingers 12 on the exterior surface of the container 23, foldablyconnected to the cylindrical side wall 24. As also seen in FIG. 5, theedges 12d and 12e of adjacent, pentagonal angular fingers 12 abut andintersect at about the center 26 of the bottom 25.

As seen in FIG. 6, the bottom 25 of the container 23 also includes aplurality of overlapping, tapered fingers 13 on the interior surface ofthe container 23, foldably connected to the cylindrical side wall 24 andoverlying the angular fingers 12. As also seen from FIG. 6, minorportions of each of the tapered fingers l3 overlap. Preferably, one ofthe tapered fingers 13' is longer than the others and overlies thecenter 26 of the container bottom 25. The other tapered fingers l3overlie or underlie portions of the one, longest tapered finger 13'. Itis particularly preferred that the one, longest tapered finger l3overlie the center 26 of the bottom 25 and that the other taperedfingers 13 merely surround the center As seen in FIG. 7, the bottom 25further includes a plurality of horizontally aligned, triangular gussetpanels 14, disposed between the'overlapping, tapered fin- 'gers 13 andthe abutting, angular fingers 12. As also preferred that the one taperedfinger 13' be pressed radially inward and upward by the means 18 eitherbefore the other fingers 12 and 13 or more rapidly than the otherfingers. Preferably, the longest tapered finger 13' is also providedwith a dab of hot melt adhesive on a portion of its surface overlyingthe center 26 of the bottom construction 25. By providing the hot meltadhesive, an additional means is provided for expeditiously assuringthat leaking and/or wicking does not occur at the center of the bottom25 of the container 23. For this purpose, any conventional hot meltadhesive can be utilized.

Because the bottom construction 25 of this application is formed from aunitary blank 10, having no cuts between the fingers 12 and 13 and thepanels 11 and 14, this bottom construction provides superiorleakresistance with reduced potential for failing due to leaking otwicking, even during prolonged exposure to liquid, paste or frozenmaterials. Furthermore, because, the plastic to plastic bonds of thebottom contruction 25 are formed from both bottom and top, preferably byheat-sealing, the thermoplastic coating tends to flow and to fill-inspaces between the fingers 12 and 13 and the gusset panels 14 throughwhich leaks might occur and also to cover any exposed paperboard edgethrough which wicking might occur.

The container 23 formed in accordance with this invention from the blankcan be filled with a wide variety of liqui, paste and frozen materials.The open end of the container can be closed with a conventional, plasticor metal lid.

It is thought that the invention and many of its attendant advantageswill be understood from the foregoing description and it will beapparent that various changes may be made in the form, construction andarrangement of the parts without departing from the spirit and scope ofthe invention or sacrificing all of its material advantages, the formhereinbefore described being merely a preferred embodiment thereof.

1 claim:

1. In a thermoplastic coated, paperboard container, provided with agenerally cylindrical side wall, an improved bottom construction,comprising: a plurality of abutting, angular fingers on the bottom,exterior surface of the container; a plurality of overlapping, taperedfingers on the bottom, interior surface of the container; each of saidangular fingers and said tapered fingers being separated by a triangulargusset panel, foldably connected to and horizontally aligned betweensaid angular fingers and tapered fingers; and said angular fingers andtapered fingers being foldably connected to said side wall.

2. The container of claim 1 wherein each of said angular fingers definesa pentagon.

3. The container of claim 2 wherein two, adjacent sides of each of saidpentagonal, angular fingers are of equal length and include an anglesuch that the sum of the angles included by said two, adjacent sides ineach pentagonal, angular finger totals 360.

4. The container of claim 3 wherein said angle included between saidtwo, equal adjacent sides in each of said pentagonal, angular fingers isequal.

5. The container of claim 4 wherein said container includes sixpentagonal, angular fingers and said included angle in each finger is 6.The container of claim 2 wherein each of said tapered fingers defines ahexagon.

7. The container of claim 1 wherein one of said tapered fingers islonger than the others.

8. The container of claim 7 wherein said one, longer tapered finger isthe only tapered finger overlying the center of said bottomconstruction.

9. The container of claim 7 wherein said one longer tapered fingeroverlies a portion of all the other tapered fingers.

10. The container of claim 1 wherein each of said triangular gussetpanels includes at least one angle that is the same.

11. A blank for a generally cylindrical, paperboard containercomprising:

a substantially rectangular panel, and

a plurality of alternating tapered fingers and angular fingers, foldablyconnected to an edge of said rectangular panel;

each of said angular fingers and said tapered fingers being separated byand foldably connected to a triangular gusset panel.

12. The blank of claim 1 1 wherein each of said angular fingers definesa pentagon.

13. The blank of claim 12 wherein two adjacent sides of each of saidpentagonal angular fingers are of equal length and include an angle suchthat the sum of the angles included by said two, adjacent sides in eachpentagonal, angular finger totals 360.

14. The blank of claim 13 wherein said angle included between said two,equal adjacent sides in each of said pentagonal, angular fingers isequal.

15. The blank of claim 12 wherein each of said tapered fingers defines ahexagon.

16. The blank of claim 10 wherein one of said tapered fingers is longerthan the others.

1. In a thermoplastic coated, paperboard container, provided with agenerally cylindrical side wall, an improved bottom construction,comprising: a plurality of abutting, angular fingers on the bottom,exterior surface of the container; a plurality of overlapping, taperedfingers on the bottom, interior surface of the container; each of saidangular fingers and said tapered fingers being separated by a triangulargusset panel, foldably connected to and horizontally aligned betweensaid angular fingers and tapered fingers; and said angular fingers andtapered fingers being foldably connected to said side wall.
 2. Thecontainer of claim 1 wherein each of said angular fingers defines apentagon.
 3. The container of claim 2 wherein two, adjacent sides ofeach of said pentagonal, angular fingers are of equal length and includean angle such that the sum of the angles included by said two, adjacentsides in each pentagonal, angular finger totals 360*.
 4. The containerof claim 3 wherein said angle included between said two, equal adjacentsides in each of said pentagonal, angular fingers is equal.
 5. Thecontainer of claim 4 wherein said container includes six pentagonal,angular fingers and said included angle in each finger is 60*.
 6. Thecontainer of claim 2 wherein each of said tapered fingers defines ahexagon.
 7. The container of claim 1 wherein one of said tapered fingersis longer than the others.
 8. The container of claim 7 wherein said one,longer tapered finger is the only tapered finger overlying the center ofsaid bottom construction.
 9. The container of claim 7 wherein said onelonger tapered finger overlies a portion of all the other taperedfingers.
 10. The container of claim 1 wherein each of said triangulargusset panels includes at least one angle that is the same.
 11. A blankfor a generally cylindrical, paperboard container comprising: asubstantially rectangular panel, and a plurality of alternating taperedfingers and angular fingers, foldably connected to an edge of saidrectangular panel; each of said angular fingers and said tapered fingersbeing separated by and foldably connected to a triangular gusset panel.12. The blank of claim 11 wherein each of said angular fingers defines apentagon.
 13. The blank of claim 12 wherein two adjacent sides of eachof said pentagonal angular fingers are of equal length and include anangle such that the sum of the angles included by said two, adjacentsides in each pentagonal, angular finger totals 360*.
 14. The blank ofclaim 13 wherein said angle included between said two, equal adjacentsides in each of said pentagonal, angular fingers is equal.
 15. Theblank of claim 12 wherein each of said tapered fingers defines ahexagon.
 16. The blank of claim 10 wherein one of said tapered fingersis longer than the others.